1. Field of the Invention
The present invention relates to thin-film magnetic recording and playback heads. More specifically, the present invention relates to thin-film magnetic recording and playback heads having a multiple-gap structure and combined read and write heads.
2. Description of the Related Art
A magnetic head for reading and writing a magnetic media operates by respectively detecting and creating magnetic domains on the magnetic recording media. The fundamental structure of a read/write head includes an magnetic material core with a small portion removed to form a gap for passing a magnetic field. The magnetic core is encircled by coils through which a current flows to induce a magnetic field in the magnetic core. In conventional magnetic heads, head coils typically include 8 to 34 turns of extremely fine varnish-coated wire. The magnetic field interacts with particles on the magnetic recording media at the gap to read and write the media. Writing of the magnetic media occurs when the electric current flows through the coil, developing a magnetic field across the gap that orients particles on the magnetic media in a pattern parallel to the direction of the magnetic flux. Reading of the magnetic media occurs when the head gap passes over a magnetic field transition, inducing a field into the magnetic core that further induces a current flow in the coil.
Thus, the magnetic head initiates write operations by supplying current to the coils and the magnetic media encodes flux transitions that are generated by the current into the head coils. Generally lower write currents are desirable since the lower currents produce less electrical stress on the magnetic head, improving head reliability.
The fabrication of conventional and composite magnetic heads involves significant piecework and manual handling of individual parts such as laborious winding of tiny coil wires around minuscule magnetic cores. The manual fabrication of conventional and composite heads is unproductive and costly. Magnetic thin-film heads have been developed to achieve high data density in magnetic media while eliminating many of the problems associated with conventional and composite magnetic heads. The fabrication of magnetic thin-film heads exploits semiconductor fabrication processes to form a large number of heads simultaneously on a common substrate or wafer. Magnetic thin-film heads are fabricated using the photochemical techniques that are conventionally employed to manufacture semiconductor chips for forming an electromagnetic slider. In the manner of thin film head fabrication, many sliders are created on a single wafer which is ultimately sliced into individual sliders. Magnetic thin-film heads are similar to conventional and composite sliders in that heads typically include air gaps and magnetic coils having 8 to 34 wire coils. Nickel-iron cores are typically used in thin-film heads.
Magnetic thin-film heads advantageously are more durable than conventional and composite magnetic heads, support lower flying heights and thus greater bit densities, and have smaller and lighter heads so improve track density and quicken access times. Thin film heads typically support track densities of 10,000 tpi and more, data transfer frequencies up to and beyond 100 Mhz, and flying heights as small as 5 micro inches.
Thin-film magnetic heads that perform both read and write operations have been previously constructed as distinct read reads and distinct write heads in the form of individual, discrete structures. The minimum spacing between heads has been a function of the number of heads that could practically be fabricated in a substrate area and the minimum physical area upon which the individual, discrete structures are mounted. Ideally, electromagnetic heads are positioned in as small an area and as closely spaced as possible to attain a high bit density, and also to reduce component size, energy consumption, and weight. Smaller and more closely spaced heads significantly increase the amount of data that is stored on a magnetic media.
What is needed is a read-write head that increases the density of data stored on magnetic media, a read-write head that is smaller in size for usage in smaller head arrays.
It has been discovered that read and write performance in a magnetic thin-film head is improved by forming a multiple-gap head with separate magnetic core and coil for a read head and a write head that are respectively designed to improve reading and writing performance.
In accordance with an embodiment of the present invention, a thin film magnetic head includes a thin-film magnetic core including a read core portion and an interconnected write core portion, a thin-film read coil encircling the read core portion, and a thin-film write coil encircling the write core portion. The read core portion has a read gap and the write core portion has a write gap. The read gap and write gap are mutually combined in close proximity in abutting sections of the read core portion and the write core portion respectively so that a magnetic medium is accessible to the read gap and the write gap simultaneously.
In accordance with another embodiment of the present invention, a thin film magnetic head includes a substrate having a planar surface, a thin-film magnetic core connected to the substrate, a thin-film read coil encircling the central pole and the read side pole, and a thin-film write coil encircling the write side pole. The thin-film magnetic core includes a read core portion and a write core portion. The read core portion further includes a read base core plate, a read top core plate, a central pole, and a read side pole. The read base core plate is formed on and parallel to the planar surface and has a central end and a read lateral end. The central pole has a base end and a top end with the base end attached to the central end of the read base core plate and extending essentially perpendicular to the read base core plate. The read side pole has a base end and a top end with the base end attached to the read lateral end of the read base core plate and extending essentially perpendicular to the read base core plate. The read top core plate has a read lateral end and a central end with the read lateral end attached to the top end of the read side pole. The read top core plate extends essentially parallel to the read base core plate and is attached to the top end of the central side pole. The read top core plate is separated by a read gap. The write core portion further includes the central pole which is shared with the read core portion, a write base core plate, a write top core plate, and a write side pole. The write base core plate has a write lateral end and a central end attached to the central pole between the base end and top end of the central pole. The write base core plate extends essentially parallel to the substrate planar surface. The write side pole has a base end and a top end with the base end attached to the write lateral end of the write base core plate. The write side pole extends essentially perpendicular to the write base core plate. The write top core plate has a write lateral end and a central end with the write lateral end attached to the top end of the write side pole. The write top core plate extends essentially parallel to the write base core plate and is attached to the top end of the central side pole. The write top core plate is separated by a write gap.
In accordance with a further embodiment of the present invention, a thin film magnetic head includes a multiple-pole, multiple-gap magnetic core, a first coil encircling a first pole of the multiple-pole, multiple-gap magnetic core to access a first gap of the multiple-pole, multiple-gap magnetic core, and a second coil encircling a second pole of the multiple-pole, multiple-gap magnetic core to access a second gap of the multiple-pole, multiple-gap magnetic core. The first coil has a greater number of turns than the second coil.
Many advantages are gained by the described thin-film magnetic recording and playback heads having a multiple-gap structure and combined read and write heads. The described structure advantageously combines read and write heads into a compact volume utilizing a single combined magnetic core. The multiple-gap thin-film head includes a read gap and a write gap that are advantageously positioned in close proximity so that a playback and recording media passes at a very small distance for both reading and writing. The multiple-gap thin-film magnetic head structure advantageously utilizes reductions in head volume, core size, and coil size of the write head and advantageously allocates conserved substrate space for usage by the read head. The number of read magnetic coils is advantageously increased with less resistance. The magnetic head thereby generates a higher-amplitude read signal since the signal is proportional to the number of turns in the coil. The design allows a larger read center pole and larger read side poles which improves the reading high-frequency response and improves read head efficiency. The multiple-gap thin-film head utilizes a read magnetic coil structure including multiple planar spiral coils, each with a limited number of turns, advantageously reducing the resistance per turn of coil, thereby increasing read signal amplitude and improving signal to noise ratio, while limiting coil resistance.
The dual-coil structure of the read head advantageously exploits a reduction of the total space consumed by dual planar coils to a minimum through usage of two coils that include the same number of turns. The equal size of the dual coils also advantageously results in the shortest total coil length, the lowest electrical resistance, and an optimum signal quality.